Characterization of a Manganese Superoxide Dismutase from the Higher Plant Pisum sativum

Abstract

A manganese-containin superoxide dismutase (EC 1.15.1.1) was fully characterized from leaves of the higher plant Pisum sativum L., var. Lincoln. The amino acid composition determined for the enzyme was compared with that of a wide spectrum of superoxide dismutases and found to have a highest degree of homology with the mitochondrial manganese superoxide dismutases from rat liver and yeast. The enzyme showed an apparent pH optimum of 8.6 and at 25°C had a maximum stability at alkaline pH values. By kinetic competition experiments, the rate constant for the disproportionation of superoxide radicals by pea leaf manganese superoxide dismutase was found to be 1.61 x 10' molar1-.second-' at pH 7.8 and 25°C. The enzyme was not sensitive to NaCN or to H202, but was inhibited by N,-. The sulfhydryl reagent p-hydroxymercuribenzoate at 1 mm concentration produced a nearly complete inhibition of the manganese superoxide dismutase activity. The metal chelators o.phenanthrollne, EDTA, and diethyldithiocarbamate all inhibited activity slightly in decreasing order of intensity. A comparative study between this higher plant manganese superoxide dismutase and other dismutases from different origins is presented.

Expression Studies of Superoxide Dismutases in Nodules and Leaves of Transgenic Alfalfa Reveal Abundance of Iron-Containing Isozymes, Posttranslational Regulation, and Compensation of Isozyme Activities

“…This band accounted for 70% of the total activity (calculated from data in Table 1) and was assigned to the MnSOD type (KCN-insensitive, H 2 O 2 -insensitive). However, its electrophoretic mobility (similar to that of plant FeSODs) and apparent molecular mass (45 kDa) are clearly different from those of typical plant MnSODs (Sevilla et al 1982).…”

Bax Regulates Production of Superoxide in Both Apoptotic and Nonapoptotic Neurons: Role of Caspases

“…However, DETCA is a nonspecific metal chelator that may affect the activity of copper-containing enzymes other than SOD1 (Kober et al , 2003; Halliwell and Gutteridge, 2007). It can also bind to other transition metals and has been reported to inhibit a MnSOD (Sevilla et al , 1982). Also, DETCA reduces CM-H 2 DCFDA loading in these cells (supplemental figure 1), likely via binding of the dye to the DETCA thiol.…”

NADH Induces the Generation of Superoxide Radicals in Leaf Peroxisomes

“…Nonetheless, in the glyoxysomal matrix Cu,Zn-SOD is present (24) whereas in soluble fractions of leaf peroxisomes Mn-SOD is found instead (24) and, if its activity is not completely inhibited, O2-cannot be detected in the experimental assays due to the catalytic scavenging of superoxide radicals by Mn-SOD. In contrast to Cu,Zn-SOD, Mn-SOD is CN-resistant (1 1) but can be completely inhibited by 2% SDS (12) and 1 mM PHMB (25), and is partially sensitive to NaN3 (25). However, preliminary assays showed that only NaN3 did not inhibit XOD while both SDS and PHMB completely suppressed the activity of this 02-generating metalloenzyme.…”